1. Field of the Invention
The present invention generally relates to a fully rotary or rotating hook for a sewing machine and more particularly, to an improved construction of a fully rotating hook for eliminating disadvantages due to rotational friction between an inner shuttle member or bobbin case and an outer shuttle member or loop taker.
2. Description of the Prior Art
In FIGS. 1 and 2 illustrating a prior art arrangement, there is shown a vertically fully rotating hook 1 which is held at a needle descending position, with an inner shuttle member or bobbin case 3 accommodated in an outer shuttle member or rotary loop taker 2. In the inner bobbin case 3, there is mounted a bobbin 11 for winding a bobbin thread therearound. The inner bobbin case 3 is stopped against rotation by an inner loop taker retaining member (not shown) which is fixed to a machine body. Along an outer peripheral surface of the inner bobbin case 3, there is formed an externally directed flange-like track projection 5 extending in a circumferential direction partially throughout the circumference. This projection 5 is fitted into an internally directed flange-like track groove 6 extending in a circumferential direction along a portion of the inner peripheral surface of the outer loop taker 2. The outer loop taker 2 may be driven for rotation in one direction about an axis by a drive means (not shown) connected to a rotary shaft 16. For rotating the outer loop taker 2 in the state where the inner bobbin case 3 is stopped from rotation as described above, a lubricating oil or the like is supplied between contact faces 4 of the track projection 5 of the inner bobbin case 3 and the track groove 6 of the outer loop taker 2 so as to reduce friction between such two elements.
In this prior art device, however, during high speed rotation of the vertical fully rotating hook 1, friction still exists between the outer loop taker 2 and the inner bobbin case 3, even when the lubricating oil or the like is applied thereto, thus resulting in abrasion of the rotary hook 1. Moreover, the thread or the like tends to be soiled by the lubricating oil, and thus it has been difficult to carry out a sewing operation smoothly in an efficient manner.